Mechanistic Investigation of Isopropanol Conversion on Alumina Catalysts: Location of Active Sites for Alkene/Ether Production

Abstract

Alcohol dehydration is of prominent relevance in the context of biomass conversion. This reaction can be efficiently catalyzed by alumina surfaces, but the nature of active sites, the mechanisms involved, and the key parameters to tune both the activity and the alkene/ether selectivity remain a matter of debate. In the present paper, isopropanol dehydration to propene and diisopropylether over γ-alumina, δ-alumina, and sodium-poisoned γ-alumina was investigated through a combined experimental and theoretical study. The experimental kinetic study shows that dehydration occurs following the same reaction mechanism on all materials, although γ-alumina activated above 450 °C exhibits the highest density of active sites and the highest global activity. Results suggest that all the reaction pathways involved in dehydration require the same set of adjacent active sites located on the (100) facets of γ-alumina. DFT transition-state calculations of the formation of propene and diisopropylether on the main terminat...